TY - JOUR

T1 - Novel Calcium sp3Carbonate CaC2O5- I4¯ 2 d May Be a Carbon Host in Earth's Lower Mantle

AU - König, Jannes

AU - Spahr, Dominik

AU - Bayarjargal, Lkhamsuren

AU - Gavryushkin, Pavel N.

AU - Sagatova, Dinara

AU - Sagatov, Nursultan

AU - Milman, Victor

AU - Liermann, Hanns Peter

AU - Winkler, Björn

N1 - Funding Information: The authors acknowledge funding by the Deutsche Forschungsgemeinschaft (DFG)-Germany (FOR2125/CarboPaT, BA4020, WI1232). B.W. is grateful for support by the BIOVIA Science Ambassador program. P.N.G., D.S., and N.S. were supported by the Russian Science Foundation (Project No. 22-23-00925). DESY (Hamburg, Germany), a member of the Helmholtz Association (HGF), is acknowledged for the provision of experimental facilities. Parts of this research were carried out at PETRA III. Publisher Copyright: © 2022 American Chemical Society.

PY - 2022/1/20

Y1 - 2022/1/20

N2 - CaC2O5-I4¯ 2d was obtained by reacting CO2 and CaCO3 at lower Earth mantle pressures and temperatures ranging between 34 and 45 GPa and between 2000 and 3000 K, respectively. The crystal structure was solved by single-crystal X-ray diffraction and contains carbon atoms tetrahedrally coordinated by oxygen. The tetrahedral CO44- groups form pyramidal [C4O10]4- complex anions by corner sharing. Raman spectroscopy allows an unambiguous identification of this compound, and the experimentally determined spectra are in excellent agreement with Raman spectra obtained from density functional theory calculations. CaC2O5-I4¯ 2d persists on pressure release down to ∼18 GPa at ambient temperature, where it decomposes into calcite and, presumably, CO2 under ambient conditions. As polymorphs of CaCO3 and CO2 are believed to be present in the vicinity of subducting slabs within Earth's lower mantle, they would react to give CaC2O5-I4¯ 2d, which therefore needs to be considered instead of end-member CaCO3 in models of the mantle mineralogy.

AB - CaC2O5-I4¯ 2d was obtained by reacting CO2 and CaCO3 at lower Earth mantle pressures and temperatures ranging between 34 and 45 GPa and between 2000 and 3000 K, respectively. The crystal structure was solved by single-crystal X-ray diffraction and contains carbon atoms tetrahedrally coordinated by oxygen. The tetrahedral CO44- groups form pyramidal [C4O10]4- complex anions by corner sharing. Raman spectroscopy allows an unambiguous identification of this compound, and the experimentally determined spectra are in excellent agreement with Raman spectra obtained from density functional theory calculations. CaC2O5-I4¯ 2d persists on pressure release down to ∼18 GPa at ambient temperature, where it decomposes into calcite and, presumably, CO2 under ambient conditions. As polymorphs of CaCO3 and CO2 are believed to be present in the vicinity of subducting slabs within Earth's lower mantle, they would react to give CaC2O5-I4¯ 2d, which therefore needs to be considered instead of end-member CaCO3 in models of the mantle mineralogy.

KW - CaCO

KW - density functional theory

KW - Raman spectroscopy

KW - spcarbonates

KW - X-ray diffraction

UR - http://www.scopus.com/inward/record.url?scp=85122747807&partnerID=8YFLogxK

U2 - 10.1021/acsearthspacechem.1c00284

DO - 10.1021/acsearthspacechem.1c00284

M3 - Article

AN - SCOPUS:85122747807

VL - 6

SP - 73

EP - 80

JO - ACS Earth and Space Chemistry

JF - ACS Earth and Space Chemistry

SN - 2472-3452

IS - 1

ER -